If I am tributing my opponent's monsters for the summon of Lava Golem, is there a period of time between the tributing of the monsters and the summon of Lava Golem where he can activate a trap card? e.g. I tribute my opponent's Blackwing - Bora and Blackwing - Sirocco. Can he activate Icarus Attack when I declare that his monsters are being tributed for Lava Golem?

No. Only effects that negate the Summon of a monster can start a chain at this point. If those effects are Spell Speed 2, then you could chain "Icarus Attack". However, even then, the two monsters are already Tributed and so you cannot Tribute them for "Icarus Attack". There is nothing you can do to save your monster once your opponent tries to Summon "Lava Golem".

If I am tributing my opponent's monsters for the summon of Lava Golem, is there a period of time between the tributing of the monsters and the summon of Lava Golem where he can activate a trap card? e.g. I tribute my opponent's Blackwing - Bora and Blackwing - Sirocco. Can he activate Icarus Attack when I declare that his monsters are being tributed for Lava Golem?

Dunno.
When you tribute summon normally, is your opponent allowed to icarus your monster you intend to tribute?

The answer is no. The minute you special it, there is no window of prevention.
Even if you solemn that SOB, you still lose your two monsters ;_;

or thats how ive been told. And ive been rulled like that multiple times. so yeah

If I am tributing my opponent's monsters for the summon of Lava Golem, is there a period of time between the tributing of the monsters and the summon of Lava Golem where he can activate a trap card? e.g. I tribute my opponent's Blackwing - Bora and Blackwing - Sirocco. Can he activate Icarus Attack when I declare that his monsters are being tributed for Lava Golem?

When you declare summon Lave Golem, your opp will be tributed immediately, nothing, even Solemn Warning/Judgment, can interrupt this.